Before two of its alleged members were arrested and charged in Australia last month, the hacker group known as TeamPCP carried out a hacking spree unlike any other in history. It tainted hundreds of open-source programs with its malware, stole developer accounts to perpetuate that software supply-chain hacking, and even released a Dune-themed self-spreading worm to automate the process, ultimately breaching more than a thousand companies.

Now Google’s threat intelligence group has revealed that during a key moment of TeamPCP’s rampage, the company’s own undercover researcher had infiltrated the group—allowing Google to monitor the hacking spree from the inside, warn breach targets, and even help disrupt the group’s attempts to exploit those victims.

In a talk at security firm SentinelOne’s LABScon research conference today, Google Threat Intelligence Group researcher Austin Larsen will present details on the company’s investigation—and infiltration—of TeamPCP amidst the group’s unprecedented, chaotic supply-chain hacking campaign. According to Larsen, Google eventually followed a trail of operational security mistakes allegedly made by one of the two Australians now accused of being leading members of the hacker group and passed on key identifying details to law enforcement. The company also received intelligence from ShinyHunters, another infamous cybercriminal group that TeamPCP partnered with, but which later turned on the supply-chain hackers. And perhaps most surprisingly, Larsen says that Google’s security subsidiary Mandiant had an undercover analyst—not himself—within the group’s inner circle from almost the beginning of TeamPCP’s time in the spotlight.

“One of our personas had been working for many months to build trust with one of the actors that was invited to join TeamPCP, and so was added to the group,” Larsen told WIRED in an interview ahead of his LABScon talk. “So essentially, almost day one, Mandiant was watching everything behind the scenes.”

The TeamPCP mole

Late last month, Ruben Ian Thomson and Louis Michael Gaebler, both Australians in their early 20s, were arrested by Australian police in a joint investigation with assistance from the FBI, charged with hacking crimes, and described by the Australian Federal Police (AFP)—in a press release that, due to Australian privacy laws, did not name them—as “principal participants” in TeamPCP. The hacker group, which seems to have first appeared online in late 2025, had made headlines with a brazen string of cascading supply-chain attacks: It repeatedly compromised open-source software to hide its malware, which then allowed it to hijack the credentials of software developers and plant its malicious code in yet another widely used tool, in a repeating cycle.

Starting this spring, for instance, TeamPCP compromised the open-source security scanner Trivy, the AI application programming interface tool LiteLLM, infrastructure of the web application security firm Checkmarx, the web app library TanStack, and the enterprise AI platform Mistral AI. Those repeated supply-chain attacks, with each enabling the group to cast its net again for more victims, ultimately allowed the hackers to breach open-source code repository GitHub, data contracting firm Mercor, and employee devices at OpenAI, the European Commission, and many others who have remained unnamed in public reporting. At times, the group deployed a worm known as Mini Shai-Hulud, named after the sandworms in Dune, to automate its hacking and scale up to even more victims. (The name also seemed to refer to an earlier Shai-Hulud worm that hackers designed to try a similar approach in September 2025, though it’s still not clear if TeamPCP or any of its alleged members were involved in that earlier intrusion campaign.)

Larsen now says that in March, just as TeamPCP was beginning its frenzied supply-chain hacking, Google’s own undercover analyst was invited to join the hackers’ inner circle. That inside source, whose name Larsen declined to reveal, was one of about 12 members of the group given access to a core chat that TeamPCP called CanisterWorm.

“You guys should understand that we pulled off the biggest supplychain [sic] maybe ever recorded in modern history,” one TeamPCP member wrote in the leaked chats.

Michael Fletcher, a former AFP analyst who now works in the threat research division of an Australian telecom firm, says he approached Larsen around that time about methods for monitoring the group’s members and activities. He says that Larsen responded by asking Fletcher to approach the hackers with caution because one of them was a “friendly,” Fletcher remembers. “I thought, damn, you all have been inside this early,” he says.

Google’s undercover analyst, Larsen says, gained access to a server where TeamPCP was storing its trove of credentials stolen from its many victims: the usernames, passwords, and access tokens it had obtained through its hacking and seemingly planned to use to extort target companies. So Google’s team decided to take action to warn victims and prevent TeamPCP’s ransom scheme. “My thought was: How can we, as quickly as possible, disrupt their campaign before more compromises can happen?” Larsen says. “Let’s go mess up what they’re doing. That was my goal.”

Rather than focus on alerting the owners of the stolen credentials at victim companies directly, which Larsen says would have taken too long given the sheer number of breached companies, Google first reached out to providers where those credentials could be used, like Amazon Web Services and Microsoft, to have the credentials revoked and prevent the hackers from exploiting them. Larsen and his team sent out hundreds of notification emails to those providers and then to victims, many of which got immediate responses.

Around the same time, Larsen says, Google’s visibility into the TeamPCP internal chat also allowed it to learn that someone within the group’s core circle was, distinct from the group’s supply-chain hacking, using an AI tool to develop a zero-day exploit in a widely used piece of login software that would allow the hackers to bypass its two-factor authentication. Google’s team got a copy of the exploit code, tested it out, and found that, with a few tweaks, it worked—a rare instance of an in-the-wild AI-created hacking technique that took advantage of a previously unknown software vulnerability. Google warned the software’s developer, who was able to patch its security flaw. (The incident was described in a case study Google released in May, but without naming TeamPCP or detailing how Google learned about the exploit.)

More betrayals, sloppy opsec

Google’s analyst was not, it turns out, the only traitor in TeamPCP’s midst.

Even prior to Google’s disruption effort, Larsen says, the group struggled to profit from its enormous collection of stolen data, which, according to the AFP, included more than half a million users’ credentials. Larsen estimates that, despite that haul, it was pulling in only tens of thousands of dollars in extortion payments, not the millions similar groups have amassed. So in an attempt to better monetize its hacking, TeamPCP invited multiple other cybercriminal groups to partner with it, giving them access to the stolen credentials in exchange for a percentage of any extortion payments they were able to extract.

One of those cybercriminal partners was ShinyHunters, a years-old, highly prolific hacker group that has extorted millions of dollars from victims through data theft and ransomware, including in the breach of educational software platform Canvas that would later paralyze thousands of schools across the US. Around April, a few weeks after partnering with TeamPCP, ShinyHunters went rogue, Larsen says, carrying out its own extortions with TeamPCP’s credentials but without giving the supply-chain hackers their cut. ShinyHunters went so far as to share with Larsen, unsolicited, a full log of the group’s chat on TeamPCP’s server—not knowing that he already had access via Google’s mole.

ShinyHunters also taunted TeamPCP in messages on X, and its louder betrayal got the latter group’s attention. TeamPCP responded by narrowing its inner circle, moving its data to a new server, and exiling ShinyHunters and several other group members from its CanisterWorm chat, including Google’s undercover analyst.

“Just delete that and stop sharing shit with shinyhunters,” one of the TeamPCP leaders wrote.

Even without that inside source, though, Larsen says more traditional digital detective work allowed him to piece together the trail of breadcrumbs that would ultimately let him learn the identity of Thomson, one of the two men charged for allegedly playing “key” roles in TeamPCP. Larsen found in a leak of user data from the BreachForums hacker forum that one of the most active handles in the CanisterWorm chat had been registered with the Gmail address sheepstealing@gmail.com. Combing through other forum archives, he found a 2019 dispute between someone with the pseudonym sheepstealing and a seller of pirated Microsoft Office keys, in which the sheepstealing user demanded a refund at a PayPal account tied to the email ruben@thomsonfamily.net.au.

After TeamPCP moved its stolen credentials to a server hosted by a different provider, Larsen says, Google was able to learn about some contents of the new server—through what Larsen describes as a “trusted partner”—and also that it was being backed up to a Google Drive on that same sheepstealing@gmail.com account.

“When we saw that, I just thought: There’s no way. Why would he be sending all of this illicit, stolen material to a Google Drive that’s tied to himself?” Larsen says. “That’s when we gave the tip to the FBI.” Larsen says he got an interested response from an agent in a matter of minutes. (Larsen may not have been alone in identifying Thomson or other alleged TeamPCP hackers prior to their arrest. Journalist and cybersecurity sleuth Brian Krebs, for instance, published a story last month laying out his own set of clues that led to Thomson’s identity.

In a statement to WIRED, the FBI declined to comment on any “active investigation” but noted that it “is able to confirm we strive to increase impact on adversaries through partnerships as documented in our newly released FBI Cyber Strategy.” The AFP declined to comment.

About a month after his tip, Larsen says, US law enforcement had finished the legal process of requesting Thomson’s data from Google with a warrant. Late last month, Thomson was arrested by Australian police, who released a video of him being walked out of a suburban home in a Northface hoodie and sweatpants.

Neither Thomson nor Gaebler, the other alleged member of TeamPCP who was arrested, could be reached for comment.

Larsen was careful to note that Google’s undercover analyst inside of TeamPCP never engaged in any illegal hacking or even encouragement of the group’s breaches. “They were a fly on the wall, only saying enough to not be suspicious,” Larsen says. “There are guardrails around what we do.”

But Larsen also notes that his team’s work to actively foil TeamPCP’s hacking is part of a new shift within Google. The investigation, after all, kicked off around the same time as Google’s newly launched Cyber Disruption Unit, which has been officially tasked with taking a more aggressive approach to combating cybercrime and state-sponsored hacking.

“Google Threat Intelligence Group has put an emphasis on disruption. That’s one of our missions now,” Larsen says. “Writing reports can only be so useful. Taking action to protect users and customers—that is the next step.”

This story originally appeared on wired.com.